The present invention relates to a method of manufacturing a large tank for use as an oil tank or a CO2 storage tank, for use in building a submerged tunnel, a submarine living quarter or a submarine station, or for use as a battery tank.
The invention also relates to a combined system for deep-sea power storage and carbon dioxide dissolution.
Further, the invention relates to a deep-sea power storage system for generating electric power by using sea water.
Still further, the present invention relates to a submarine power storage system which is installed in the deep sea and which stores electric power by utilizing the pressure of sea water.
Moreover, this invention relates to a submarine storage system designed to store, for example, LNG.
Furthermore, the present invention relates to a method of building a submerged tunnel for drive ways and railroads, which runs on the seabed.
Conventionally, a submarine tank is built on land, in a horizontal position in a dock large enough to hold the entire tank.
A system may be constructed by using as large a tank as possible, for example, a cylindrical tank having a diameter of 100 m and a length of 400 m. Building of such a large tank on land is subjected to various restrictions. Hence, tanks that can be built on land are limited in size.
More specifically, if a large tank is manufactured on the land, its size is limited by the size and proof strength of the dock, and also by the draft of the dock and the depth of the neighboring water passages.
An object of the invention is to provide a method which can manufacture a tank that is too large to be built on land.
Such a large tank finds use in, for example, thermal power plant. A thermal power plant is located near the seacoast in most cases. The carbon dioxide gas (carbon oxide gas) generated in the thermal power plant will result in environmental disruption such as air pollution. Attempts have been made to dissolve the gas in sea water and thereby discard the gas, by using various methods.
More precisely, (1) a method of dissolving the carbon dioxide gas generated in the thermal power plant, directly in sea water; (2) a method of solidifying the carbon dioxide gas into dry ice and sinking the dry ice onto the sea bottom: and (3) a method of liquefying the carbon dioxide gas aboard a ship and dissolving the gas in the sea water, over a sea zone 1000 m wide.
With the method (1) it is difficult to dissolve the carbon dioxide gas sufficiently. Furthermore, there exists the danger that the carbon dioxide gas blows up over the sea surface.
The methods (2) and (3) may render the sea water strongly acid. This is because the liquefied or solidified carbon dioxide is dissolved in the sea water, inevitably increasing the carbon dioxide concentration in the sea water, making the sea water strongly acid.
Consequently, the methods (2) and (3) affect the deep-sea life. The methods (2) and (3) may also induce environmental changes because it lowers the temperature of sea water. Further, a great amount of energy is required to perform the methods (2) and (3), in which carbon dioxide is solidified into dry ice and liquefied, respectively.
The present invention has been made in view of the above. An object of the invention is to provide a combined system for deep-sea power storage and carbon dioxide dissolution, which can store power, causing no cavitation of a high-head pump turbine, and which can dissolve and discard carbon dioxide at low cost, not affecting marine ecology or causing environmental changes.
The conventional power system is disadvantageous in the following respect. Hitherto known is a pumped storage power system in which water is pumped up at night by using surplus electric power, and electricity is generated in the day when the power consumption is at its peak. However, geographical conditions for a pumped storage power system are restrictive, and the building cost of the system is increasing much. In view of this, it has become difficult to construct new pumped storage power plants.
Recently a deep-sea power storage system has been proposed as a low-cost power plant. This system has less restriction on its geographical conditions, and can be constructed at low cost. The system comprises a main body and a battery tank. The main body, which has a pump turbine, is installed in the deep sea, together with the battery tank. At night, the surplus power generated on land is used to turn the pump turbine, thereby discharging sea water from the battery tank, and power is stored by virtue of the energy obtained from the water head between the sea level and the sea water level in the battery tank.
In the day when the power consumption is at its peak, sea water is poured into the battery tank, thereby turning the pump turbine and generating electric power, and the power thus generated is supplied to the land.
Jpn. Pat. Appln. KOKAI Publication No. 04-01940 based on a patent application, for example, in which the present applicants are named as inventors, discloses a deep-sea power storage system. In this system, sea water is introduced into the pressure-resistive vessel laid in the deep sea (usually, on the seabed), rotating the water turbine. The water turbine drives the generator, which generates electric power. The power generated is supplied to the land. In the system, the surplus power available on the land is used to drive the water turbine, pumping the sea water from the pressure-resistant vessel, thereby to store the electric power.
Studies must be conducted for the foundation of such a deep-sea power storage system, which is strong enough to withstand earthquakes. This is because earthquakes may happen at the seabed on which the system is installed.
Measures should be established that must be taken to repair the various components of the system, such as the pump turbine, if troubles should develop in these components in the deep sea. Furthermore, measures should be established that must be taken in case cavitation takes place. Cavitation is likely to happen when a vacuum similar to water vapor develops in the space above the sea water level in the battery tank as the pump turbine discharges the sea water from the tank.
The present invention has been made in view of the above. An object of the invention is to provide a deep-sea power storage system which is greatly resistant to vibration, which can easily be repaired, and which can operate reliably.
A conventional submarine power storage system is installed, with the battery tank and electrical/mechanical component cases (containing power-generating equipment, power-storing equipment and the like) provided and secured within the pressure-resistant vessel.
Therefore, an additional pressure-resistant vessel must be used in order to increase the output of the system a little, if necessary to meet an increased demand for electric power. In fact, it would be extremely difficult to satisfy such a demand as described above.
In the case of a pumped storage power plant constructed in a mountainous region, which utilizes the head of a water storage dam, the amount of power it can store is determined by the capacity of the dam. With this plant it is difficult to store more electric power.
In view of this, the present invention has been made. An object of the invention is to provide a submarine power storage system that can have its storage capacity increased even after the commercial operation.
There is the trend of stockpiling LNG, just like petroleum. The annual domestic consumption of LNG is about 55,000,000 m3 at present. If LNG were to be stored for 120 days of consumption, like petroleum, it should be stored in an amount of 18,000,000 m3.
In order to store this amount of LNG, 90 LNG tanks are necessary, each capable of storing 200,000 m3 at most. At present there is no land large enough to build so many tanks. From an economical point of view, too, it is difficult to build these tanks.
It would be dangerous, as is pointed out, that LNG tankers frequently navigate along a gulf coast where thermal power plants are densely constructed, because the LNG tankers may likely to collide with each other.
Hitherto, LNG has been stored in LNG tanks built on the ground or half-buried in the ground. The LNG tanks must be made of press-stressed concrete or high-density reinforced concrete to acquire a press stress and withstand the inner pressure. The use of either material complicates the structure of the LNG tanks. This renders it difficult, from an economical viewpoint, to build LNG tanks of this type.
More precisely, a press stress must be applied to the conventional LNG tanks to prevent a tensile stress from developing even if the inner pressure of the tanks rises. In order to apply a press stress to the tanks, reinforcing bars and tendons are embedded in concrete, extending vertically and horizontally. This inevitably makes the tanks complex in structure.
Moreover, LNG acquires a pressure nearly equal to the atmospheric pressure when it is used. It must therefore be maintained at xe2x88x92162xc2x0 C. to assume a liquefied state at the atmospheric pressure. This is an absolute requirement that must be fulfilled to attain safety. This maintenance of temperature is a hindrance.
Namely, energy should be used to accomplish forced cooling in order to maintain the gas at xe2x88x92162xc2x0 C. or less for a long time under the actually applied pressure equal to or less than the atmospheric pressure.
Furthermore, a pump immersed in the LNG contained in an LNG tank is operated, forcing LNG cooled to xe2x88x92162xc2x0 C. out of the LNG tank and supplying the same. Once a trouble has developed in the pump immersed in LNG, the plant cannot help but be stopped. The pump is, as it were, a lifeline to the plant.
Geographical, economical, cooling and LNG-supplying conditions for an LNG storage system can hardly be satisfied. As a matter of fact, it has hitherto been considered to be difficult to reserve (store) LNG for so long a time as petroleum.
This present invention has been made in view of the above. An object of the invention is to provide a submarine LNG storage system which can be constructed near cities and which can store LNG in great quantities for a long period of time.
Today, tunnels are dug in the seabed, thereby constructing roads and railways, thus providing routes connecting locations on the land.
The technique using a shield machine is employed to build tunnels in the seabed. In the course of building a tunnel in the seabed, large-scale measures must be taken to stop dead water. Besides, it usually takes a long period of time to dig the tunnel in the seabed.
Recently, so-called submerged tunnel technique has come into practical use. This technique is to submerge tunnel units made of concrete in the sea and connect the units in series on the seabed, thereby building a submerged tunnel. With the submerged tunnel technique it is easy to stop dead water. Further, the technique can build a tunnel within a short period of time.
The submerged tunnel technique is carried out as follows. First, concrete tunnel blocks of the type shown in FIG. 45 are made on the ground, each having passages for roads or railways. Then, the tunnel blocks are towed by tugboats to a building site on the sea, submerged there in the sea, anchored on the seabed and connected in series, thus building a submerged tunnel.
Very recently it has been proposed that big and long tunnel blocks, each having roadbeds and railway tracks, be used to build a submerged tunnel on the seabed. A large-scale transport route can thereby be provided.
It is difficult, however, to manufacture such gigantic tunnel blocks on the ground, for some reasons. A large land area is required, and a transport equipment (hoisting system) must be provided. To make matters worse, the manufacturing efficiency is low since the manufacture site extends horizontally and is considerably spacious.
Furthermore, manufacturing tunnel blocks on the ground requires much cost and many man-hours. This is because concrete needs to be deposited in a great amount in order to form the horizontal sections of each tunnel block, and also because many reinforcing members must be laid before concrete is deposited to manufacture each tunnel block.
Also, additional reinforcing members must be used to prevent a tensile stress from developing in the concrete sections while the tunnel block is being made on the ground. More specifically, unless reinforcing bars are laid for preventing a tensile stress, after a block of steel plates has been made, concrete can not be deposited in the steel shell.
This means a reinforcing frame needs to be assembled twice. A considerably high cost and a number of man-hours are required only to deposit concrete.
Due to these facts, it is regarded as impossible to manufacture big and long tunnel blocks on the ground. Further it is considered difficult to shorten the time of building a submerged tunnel. These hinder the construction of a large-scale submerged tunnel.
In view of this, the present invention has been made. Its object is to provide a technique of building a large-scale submerged tunnel within a short period of time, by using huge concrete tunnel blocks which can be manufactured at low cost.
According to a first aspect of the invention, there is provided a method of manufacturing a large tank, which comprises the steps of:
constructing a floating base on the sea, surrounding a first spherical shell section constituting one end of a tank;
building a hollow cylindrical section on the first spherical shell section, in the floating base; and
attaching a second spherical shell section to the hollow cylindrical section, closing an open end thereof.
According to the invention, the vast space available on the sea and in the sea can be utilized in manufacturing the tank, because the large tank is partly submerged in a vertical position while being manufactured. Restriction is not imposed, which would be inevitably imposed if the tank were built in a dock on the ground.
As a result, a large tank having a diameter of, for example, 100 m or more, can be manufactured.
The tank thus manufactured on the sea can be easily installed on the seabed in a horizontal position. Namely, it suffices to pour water into the tank, while pulling the tank by tugboats, thus inclining the tank into a horizontal position, then to tow the tank to the installation site, further to pour water into the tank, thereby submerging the tank in the horizontal position, and finally to mount the tank on the tank base already secured to the seabed.
If it is predicted that high waves come due to typhoon, the tank and the floats surrounding the tank may be submerged into the sea, by pouring water into their ballast tanks. Once in the sea, neither the tank nor the floats would be affected with winds or waves.
According to a second aspect of the invention, there is provided a combined system for deep-sea power storage and carbon dioxide dissolution, which comprises:
a tank which is installed on a seabed, into which sea water is poured, from which sea water is discharged, and which has a high-head section and a low-head section;
an electrical/mechanical component containing unit arranged on the seabed and adjacent to the tank, containing a low-head pump turbine into and from which sea water from the high-head and low-head sections of the tank flows, and a high-head pump turbine into and from which sea water flows from the high-head section of the tank and from a deep sea; and
a carbon dioxide pipeline for supplying carbon dioxide from the ground into the sea water contained in the tank.
In the combined system for deep-sea power storage and carbon dioxide dissolution, sea water is supplied into the tank located in the deep sea, turning the high-head pump turbine and the low-head pump turbine provided in the electrical/mechanical component containing unit. Hence, the system can generate electric power.
Furthermore, sea water is discharged from the tank into the deep sea through the electrical/mechanical component containing unit. In the tank, the water from the high-head section into the inlet port of the high-head pump turbine, into which sea water flows from the deep sea. This prevents the carbon dioxide dissolved in the sea water from changing into gas, and thus preventing cavitation of the high-head turbine.
In addition, a great amount of carbon dioxide can be dissolved in the sea water contained in the tank by supplying carbon dioxide or liquefied carbon dioxide into the tank from the ground through the pipeline.
Thereafter, the sea water is discharged from the tank into the deep sea, whereby carbon dioxide is diluted. Hence, carbon dioxide can be discarded without raising the acidity of sea water around the combined system or lowering the temperature of the sea water.
The combined system for deep-sea power storage and carbon dioxide dissolution can store power in the deep sea, without causing cavitation of the pump turbines, and can dissolve and discard carbon dioxide at low cost, without raising the acidity of sea water or lowering the temperature of the sea water. The combined system would not affect marine ecology. Nor would it cause environmental changes.
According to a third aspect of the invention, there is provided a deep-sea power storage system which comprises:
a mound constructed on a seabed;
a system body having a battery tank and an electrical/mechanical component container containing at least a pump turbine and a generator/motor;
a unit base provided on the mound and supporting the system body; and
a shock-absorbing member interposed between the mound and the unit base.
According to a fourth aspect of this invention, there is provided a deep-sea power storage system of the type described above. This system is characterized in that shock-absorbing member is made of hard rubber.
According to the third and fourth aspects of the invention, the vibration generated due to a submarine earthquake is not transmitted to the system body, thanks to the shock-absorbing member (hard rubber) interposed between the mound and the unit base which supports the system body.
According to a fifth aspect of the invention, there is provided a deep-sea power storage system of the type described above. This system is characterized in that the battery tank and electrical/mechanical component container is capable of floating on the sea.
According to the fifth aspect of the invention, the battery tank and the electrical/mechanical component container, which constitute the system body, can be floated to the sea level whenever necessary. This facilitates the repair and maintenance of the system body.
According to a sixth aspect of the present invention, there is provided a deep-sea power storage system of the type described above, which is characterized in that the battery tank is arranged with a lower surface located above the pump turbine contained in the electrical/mechanical component container.
In this system, the lower surface of the battery tank mounted on the unit base remains at a level above the pump turbine. A sufficient head is thus always secured at the inlet of the pump turbine, preventing cavitation of the pump turbine. This ensures a stable operation of the system.
According to a seventh aspect of the invention, there is provided a submarine power storage system which comprises:
a unit base connected by a submarine cable to a ground facility, having a plurality of container seats including spare seats, and equipped with electrical connecting pipes, connecting pipes and the like;
a plurality of electrical/mechanical component containers mounted respectively on the container seats excluding the spare seats, each of the containers containing a turbine, a generator a motor, a pump and the like; and
a plurality of battery tanks connected by the connecting pipes to the electrical/mechanical component containers, respectively, and having a sea water inlet/outlet port each.
According to an eighth aspect of this invention, there is provide a submarine power storage system of the type described above, which is characterized in that each of the battery tanks has a connecting pipe detachably connected to the connecting pipe of a pipe coupling section provided on the unit base.
According to a ninth aspect of the invention, there is provided a submarine power storage system of the type described above. This system is characterized in that the unit base has a plurality of container seats including spare container seats and tank seats including spare tank seats. It is also characterized in that the battery tanks are mounted directly on the unit base, and in the unit base the battery tanks are connected to the turbines contained in the electrical/mechanical component containers.
According to a tenth aspect of the invention, there is provided a submarine LNG storage system comprising:
an LNG supply station provided on the ground or on the sea;
a large concrete storage tank installed on a seabed and connected to the LNG supply station by a gas pipeline and a liquid pipeline, for storing the LNG supplied from the LNG supply station through the gas pipeline and the liquid pipeline;
pump means for introducing a part of high-pressure gas generated in the LNG supply station, into an upper space in the storage tank through the gas pipeline, thereby to apply a pressure on the LNG contained in the storage tank and to pump the LNG upwards to the ground through the liquid pipeline; and
cooling means for drawing gas from the upper space in the storage tank through the gas pipeline, thereby to cool the LNG stored in the storage tank.
Since the storage tank is installed on the seabed and stores LNG supplied from the LNG supply facility on the ground or on the sea. Nor particular location restrictions are imposed on the storage tank. In other words, the storage tank can be installed on the seabed near a city.
Once the tank is installed on the seabed, an external compressing force that depends on the depth where the tank is located is applied on the tank. The tank therefore assumes the same state as a pre-stressed tank. No tensile stress generates in the concrete section of the storage tank even if the inner pressure rises to the same value as the external pressure. The tank is simple in structure, not having a special pre-stressed structure. This solves an economical problem.
When the gas in the upper section of the tank is drawn through the gas pipeline, the LNG evaporates from the storage tank. More specifically, the amount of LNG that should be evaporated from the surface of LNG, taking the latent heat of evaporation and, thus, cooling the liquid phase. The gas can be completely cooled to remain in liquid phase without using extra energy.
That is, a cooling system is constituted in the tank, which takes by itself the heat of evaporation from the surface of the LNG, thereby cooling the liquid phase of natural gas. The cooling condition required is thus satisfied. The cooling efficiency can, of course, be controlled by changing the flow rate of the gas.
A part of the high-pressure LNG gas generated in the LNG supply facility is supplied into the storage tank on the seabed through the gas pipeline. A pressure is thereby applied on the surface of the liquid in the tank, too. As a result, the LNG is pumped up to the ground through the liquid pipeline, which extends from the lower part of the tank.
Though not incorporating pumps, which are liable to malfunction, the tank has a pump system that pumps LNG autonomously. The conditions for pumping LNG are satisfied.
Controlling the amount of the gas can of course change the rate of pumping LNG. The LNG is thus pumped, because the tank is installed on the seabed and has a high pressure-resistance.
According to an eleventh aspect of the present invention, there is provided a method of building a submerged tunnel, which comprises the steps of:
manufacturing hollow cylindrical concrete tunnel blocks, each having both ends closed by spherical shell covers, while partly submerging the tunnel blocks in the sea in a vertical position such that a work platform remains at a predetermined level above the sea level;
submerging the tunnel blocks into the sea and arranging the tunnel blocks in series on a seabed;
connecting the tunnel blocks, while sealing circumferential walls of any two adjacent tunnel block from each other by means of a seal member;
draining water from a junction between any two adjacent tunnel blocks by discharging water from a closed space defined by the seal member and the opposing spherical shell covers of the tunnel blocks; and
removing the covers, thereby making the tunnel blocks communicate with one another.
In this method, the tunnel blocks are assembled gradually on the sea, making good use of their buoyancy. A vast space available on the sea can therefore be utilized to manufacture tunnel blocks.
The method can build a large-scale submerged tunnel which has a driveway floor and a railway floor.
Furthermore, the site of manufacturing hollow cylindrical tunnel blocks is compact and small since the blocks are built, while being partly submerged in the sea in a standing position. This helps to enhance the manufacturing efficiency.
Partly submerged in the sea and set in a vertical position while being manufactured, the tunnel blocks excel in not only manufacturing cost but also in the number of man-hours required.
Namely, it suffices to deposit a small amount of concrete into the horizontal parts of each tunnel block, because the block is gradually submerged into the sea as it is manufactured. Further, reinforcing members which must be used to deposit concrete to build a tunnel block on the ground need not be employed at all, because the concrete section of the block, submerged in the sea, receives a compressing stress from the sea water.
Furthermore, the tunnel blocks not only excel in pressure-resistance and outer appearance, but also are simple in structure, not using reinforcing bars. This is because the blocks remain compressed while being manufactured. They may have, for example, steel-concrete structure, each composed of only steel plates and high-strength concrete.
Hence, it can be expected that a large-scale submerged tunnel be built at low cost and within a short time, though the tunnel blocks are long and huge ones. Moreover, the construction of the tunnel can be started at any point in the planned route or at two or at more points at the same time, because the tunnel blocks can be manufactured simultaneously on the sea. This helps shorten the time required for building the submerged tunnel.